4. History of Polyurethanes
• Dr. Otto Von Bayer (1937)
•IG Farben
Industries
•Rigid and flexible
foams
•TDI and polyols
•Attempts to
reduce natural
rubber use
5. What are Polyurethanes?
•Polyurethane
•Polyurethane polymers are traditionally and most
commonly formed by reacting a di- or
polyisocyanate with apolyol. Both the isocyanates
and polyols used to make polyurethanes contain on
average two or more functional groups per molecule.
10. Polyurethane Reactions
•Multiple types of reactions make up
different end products of polyurethanes
•Polyurea reactions are important for
spandex production
14. Components of Polyurethanes
• Isocyanates
• Polyol
• Catalysts
• Silicon surfactant
• Fire retardant
• blowing agent
15. Isocyanates;
Different Isocyanates are used for the
synthesies of polyurethane. Toluene
diisocyanate (TDI) was the first mass produced
isocyanate. It was used for rigid and flexible
products before the development of Methyl
phenyl diisocyanate (MDI) in the early 1960s.
TDI is still used in most flexible foam and many
elastomers and coatings. The TDI production
process yields two difunctional isomers
16. . The series of multifunctional aromatic or
aliphatic isocyanates are used in polyurethane
foams. The detail information about synthesis
and reactions of isocyanates can be studied in
the literature. Polyurethane is commercially
produced by the phosgenation of amines. The
solution of amine and phosgene are mixed to
form a slury of amine hydrochloride and
carbamic chloride then by heating the amine
salts react with excess phosgene.
17.
18.
19. Parameter Value
Colour Dark brown
Viscosity (CPS) 170-250
Specific Gravity at 25
degree centigeade
1.24
NCO content 32
Specification of Crude MDI
20. Molecular Weight 174.163
Density (g. per cm3) @20°C
(68°F)
1.21
Viscosity (cs) @100°C (212°F) 0.8
Freezing/Melting Point
Range T100 (°C)
21.5-22.0
Freezing Point 2,4-isomer
(°C)
15.0
Boiling Point @10mm Hg (°C) 121
Flash Point, COC (°C) 132
Acidity, as HCI (%) T100 <0.0130
Specification of TDI
21. Polyols
During the initial development of
polyurethanes, polyesters were the most
commonly used type of Polyols. Since
unsaturated polyesters were found unstable
for use in polyurethanes, completely
saturated polyesters containing terminal
hydroxyl groups rather than carboxyl groups
are used many Polyols are available to the
polyurethane formulator. The size,
functionality, and starting materials
determine the properties of the final
product.
22. Rigid polyurethanes are formed by low molecular
weight polyol.
Flexible polyurethane are make from the higher
molecular weight polyols, castor oil, trihydroxy fatty
triglyceride, is an example of naturally occurring
polyol.
Polyester polyols are prepared by step growth or
condensation polymerization. Formation of polyester
chains is a random process and leads to broad
distribution of molecular weights. Bifunctional
monomer make the linear polymers.
23. Adipic acid used where flexibility is required,
The Phthalic anhydride is used for those
requiring rigidity, Dioles include ethylene
glycol, 1.4 butandiol. And 1,6- hexandiol The
polymerization has the characterstics of a
chain reaction, whose chemistry is presented
by initation, propagation and termination
steps. Propylene oxide (PO) and ethylene
oxide(EO) , are low price epoxides produce by
the oxidation of proplylene and ethylene.
24. Polyols
•Polyols are the major component of rigid
polyurethane. Rigid polyurethane foam can be
manufactured by standard polyether base and
polyester base polyol.
25. Type of PU average
molecular
weight
OH no(mg
KOH/gram)
Average
functionalit
y
Viscosity
at 25
degree
centigrate
(CPS)
Acid
number
Density(gm/cm)
Rigid foam 930 350-390 6.2 1500-
3000
1.0 1.1
Shoe sole 2000 58-62 2.1 700-1000 0.4 1.15
Elastomers 2000 50-58 2 500-800 1 1.17
Soft coating 2750 38-45 2 700-800 1 1.12
Hard coating 2450 250-270 11.3 17000 4 1.24
Flexible foam 2400 57-63 2.7 1000-
1200
1.3 1.15
26.
27. Catalysts
Catalyst is the important additive. It is control
the reaction rate and also control the balance
between polyol and isocyante reactions. and
blowing in order to attain the desired foam
properties.
Amine and Tin are two good catalyst used.
Formation of transient complexes between
polyol and isocyanate are formed due to
catalyst.
28. Tertiary amines can catalyze both in gelling and
blowing reaction and are usually called the blowing
catalysts, Reaction rate of both gelling and blowing
process depend on catalyst structure.Amine catalyst
are control the both these parameter.
Tin catalyst are more reactive and use in less
quantity but it is use for gelling reaction, so it is
called the gelling catalyst. .
29. Surfactant
•It is important additive in polyurethanes to get
homogenous foam with low density,
•Surfactant help in good mixing during foaming.it can
prevent bobbles from collapse and stabilize the cell
structure. Branching chains can be introduced to
either silicone or polyether and different end group
can be cooed in to chain end.
30. Blowing agent
Different blowing agents are used to form gas
bubbles in the reaction mixture Firstly water was
used as a blowing agent then it was rejected due
to high boiling point and open cell foam is
produced which was not good for insulation. In
insulation we need low thermal conductivity
material but the polyurethane which is
manufactured by water has high thermal
conductivity. Now CFCs, HCFCs, Pentanes, HFCs
are use as blowing agent in rigid PU foam these
gases are responsible for excellent insulation
properties
31. CFCs gases were phased out due to environmental
problems. In japan & Europe CFCs-11 was
substituted by HCFCs 141b are Pentanes. middle
East Asia and Africa CFCs-11 is still used.
32. Blowing
agent name
Molecular
weight
gm/mole
Boiling point
In centigrade
Liquid
Density at 20
degree C
Ozone
depletion
potential
CFC-11 137.4 23.8 1.49 1
HCFC-141b 116.9 32.2 1.24 0.11
HCFC-22 86.5 -40.6 1.21 0.055
HCFC-142b 100.5 -9.8 1.10 0.065
Physical properties of different blowing agents
34. Economics
•The PU industry was estimated to produce 13.65
million tons of plastic in 2010 and is expected to
grow to 17.95 million tons by 2016
•The PU industry is expected to grow from $33
billion in 2010 to $55.5 billion in 2016.